<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>弹出框</title>
  <style>
    * {
      padding: 0;
      margin: 0;
    }

    body {
      width: 100%;
      height: 100%;
      background: #fff;
    }

    .toggleModal {
      padding: 10px 20px;
      color: white;
      background: #409EFF;
      border: none;
      box-shadow: 2px 3px 20px rgba(0, 0, 0, 0.2);
      position: absolute;
      left: 50%;
      top: 50%;
      transform: translate(-50%, -50%);
    }

    .mask {
      position: absolute;
      top: 0;
      bottom: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background: rgba(0, 0, 0, 0.4);
      z-index: 100;
      display: none;
    }

    .modal {
      position: absolute;
      top: 50%;
      left: 50%;
      width: 400px;
      transform: translate(-50%, -50%);
      border-radius: 5px;
      background: #fff;
      box-shadow: 2px 3px 20px rgba(0, 0, 0, 0.2);
      z-index: 120;
      display: none;
    }

    .modal .modal-header {
      height: 50px;
      border-bottom: 1px solid #f5f5f5;
      padding: 0 15px;
    }

    .modal .modal-header p {
      line-height: 50px;
      display: inline-block;
    }

    .modal .modal-header .title {
      font-size: 18px;
      color: #333;
    }

    .modal .modal-header .close {
      float: right;
      font-size: 26px;
      margin-top: -2px;
      color: #9C9FA4;
      cursor: default;
    }

    .modal .modal-content {
      min-height: 100px;
    }

    .modal .modal-footer .btn {
      padding: 0 20px;
      height: 36px;
      line-height: 36px;
      color: white;
      background: #409EFF;
      border: none;
    }

    .modal .modal-footer {
      border-top: 1px solid #f5f5f5;
      padding: 15px;
      text-align: right;

    }

    .container::after {
      content: "";
      display: block;
      clear: both;
    }
  </style>
</head>

<body>
  <div class="container">
    <div>
      <button class="toggleModal" id="toggleModal">触发遮罩层</button>
    </div>
    <div class="modal">
      <div class="modal-header">
        <p class="title">这是弹出层的标题</p>
        <p class="close">×</p>
      </div>
      <div class="modal-content">
      </div>
    </div>
    <div class="mask"></div>
  </div>
  <script>
    window.onload = function () {
      // 获取需要使用到的元素
      var toggleModal = document.getElementById("toggleModal");
      var container = document.getElementsByClassName("container")[0];
      var mask = document.getElementsByClassName("mask")[0];
      var modal = document.getElementsByClassName("modal")[0];
      var closes = document.getElementsByClassName("close");
      toggleModal.onclick = show;
      closes[0].onclick = close;
      closes[1].onclick = close;

      function show() {
        mask.style.display = "block";
        modal.style.display = "block";
      }

      function close() {
        mask.style.display = "none";
        modal.style.display = "none";
      }
    }
  </script>
</body>

</html>